The present invention relates in general to low frequency carrierband multi port signal couplers. More particularly, the invention pertains to multi port couplers that are characterized by improved isolation, particularly between ports of the coupler, as well as having improved impedance matching characteristics.
Reference is made to the assignee's U.S. Pat. No. 4,419,636, granted Dec. 6, 1983, on a low frequency wide band signal coupler.
Carrierband local area networks are designed to provide single channel, low cost communication networks, for use in, for example, factory automated environments. These networks are primarily intended to be used as a local sub network, typically supporting thirty to sixty nodes of communication. One problem with existing networks is that they are unduly complex in construction, requiring relatively complex and costly circuitry. Furthermore, existing networks do not provide proper impedance matching and, in particular, do not provide proper isolation between tap port of the network.
Accordingly, it is an object of the present invention to provide an improved low frequency carrierband multi port signal coupler that is characterized by a well maintained isolation loss between tap ports.
Another object of the present invention is to provide an improved multi-port coupler that has proper transmission line impedance matching so as to minimize any reflection that may occur along any point of the transmission medium.
A further object of the present invention is to provide a multi port coupler employing a hybrid transformer coupling circuitry that is effective in reducing the component count significantly while at the same time providing reliability and high performance.
Still another object of the present invention is to provide a low frequency carrierband multi-port multi-directional coupler having wide band-width signal coupling, such as from 500 kilohertz (KHz) to 30 megahertz (MHz).
Another object of the present invention is to provide an improved low-frequency carrierband multi-port signal coupler that is characterized by providing an appropriate amount of RF energy from the main transmission line to each tap port with a minimum insertion loss introduced into the main transmission line.
Still another obJect of the present invention is to provide a low frequency multi-port coupler that is provided with DC isolation between the center conductor of the trunk and the taps. This provides a substantially improved noise immunity.